This invention relates to the alignment of a patient's dental occlusion and more particularly to a method and tool for alignment of mandibulary and maxillary arches containing natural dentition.
It is important in dentistry to be able to provide for the patient an ideal dental occlusion. When the teeth bite together, the condyles of the mandible should be guided into the fossa of the temporoman dibular joint in an ideal postural position. This is called centric relation. Some dentists become very good at manipulating the mandible with their hands into the ideal centric relation. This manipulation is an inexact art that is difficult to teach. It would be desirable to have a mechanical way to aid the dentist in this manipulation process.
A device called the Gothic-arch tracer has been used successfully in full-denture construction, as shown in FIGS. 1 and 2. In the edentulous patient, the upper and lower base plate 10, 16 is fitted to the edentulous ridges as a first step in denture construction. The lower base plate can carry the tracing pin 18 and the upper can carry the tracing plate 12. The Gothic-arch kit, with the component parts necessary for this full-denture technique, can be obtained from: Blue Dolphin Products, Concord Circle, Unit #1, Morgan Hill, Calif. 95037.
This Gothic-arch tracer has a tracing pin 18, which is usually attached by a support plate 20 into the lower dental arch. This pin occludes upon a striking plate or tracing plate secured into the upper arch. The pin can have some means to mark the upper plate as the mandible moves, while maintaining pressure on the upper plate. This produces tracing lines 14 on the tracer plate 12, which represent the movement patterns of the mandible.
The mandible is limited in its movements by the ligaments, muscles, and hard tissue of the temporomandibular joint. Movements of the mandible, marking the most extreme limited positions, are said to be border movements. When the Gothic-arch tracer inscribes lines on the upper plate, while moving from the most retruded position forward and laterally in the extreme border pattern, the tracing lines often take the shape of a Gothic arch, thus the name Gothic-arch tracer.
The apex of the Gothic-arch tracing represents the most retruded border position of the mandible. This point is called centric, and the mandible retruded into the centric point is said to be in centric relation.
When the teeth bite together in the most extreme closed position, they are said to be in centric occlusion. Many dentists believe that when the teeth are in centric occlusion, the mandible should be guided into the most retruded centric-relation position. When the centric position is located, it can be used to construct a bite-registration fixture, to be used to mount casts of the dental arches on the lab articulator, which simulates the patient's mouth. Dental appliances can then be constructed on the mounted cast. The occlusal biting surfaces of appliances constructed on such mounted casts will then guide the mandible in centric relation when seated in the mouth. The Gothic-arch mechanism can also be used to adjust the occlusion directly in the patient's mouth.
A device and method for using the Gothic-arch tracer in the natural teeth are described in U.S. Pat. No. 5,722,828 (Halstrom). The device described provides for bite rims fitted over the natural teeth, and secured with dental-impression material contained within the rims. These rims have a tracer screw and tracer plate mounted on arms which extend forward outside of the mouth. When the tracing is done, the two units are locked together in centric position, and removed from the mouth. Dental casts are then inserted into the resilient impression material for mounting on an articulator. The procedure is very time-consuming. The appliance is bulky. Placing the cast into the impression material in the rims can be less than accurate. The appliance, which covers the occlusal surface of the teeth, requires that the bite registration be taken with the teeth in an open-bite position. It is unable to take the bite registration in a nearly closed-bite position, i.e., with the occlusal surfaces of the teeth in a barely-missing-contact position.
Accordingly, a need remains for a better way to determine proper bite registration in a patient having natural teeth.